This is a longitudinal study of tooth wear using a nonhuman primate model. Two groups of animals (green monkeys or vervets) are to be used in this study and they are already being raised on different diets for a study of craniofacial growth and masticatory function at the Case Western Reserve University School of Dentistry. Baseline data (e.g., dental impressions, SEM micrographs) have already been collected through an NIH post-doctoral fellowship. Dental impressions will continue to be taken at six-week intervals, and the resultant replicas will be used in quantitative scanning electron microscope analyses of dental microwear and stereophotogrammetric analyses of the overall rate and form of tooth wear in these animals. Microscopic and macroscopic changes in shearing crest, cusp, and basin morphology will be measured. The two major questions to be asked in this study are: how does tooth wear occur at the microscopic and macroscopic levels, and how does tooth use change through time as tooth wear progresses? Three lines of evidence will provide answers to these questions: (1) interrelationships between the measured microscopic and macroscopic wear features, (2) comparisons between the different dietary groups, and (3) information on craniofacial growth, bite force, and bone strain being collected through the C.W.R.U. School of Dentistry study. The results of this quantitative longitudinal study will bring a much clearer perspective to the question of the functional significance of primate tooth morphology. This study also benefits by being able to correlate the changes in tooth wear with the changing shape of the craniofacial region as indicated by a variety of measurements taken from the face and skull of the same animal subjects.